1. Field of the Invention
The present invention relates to a fluid shear coupling apparatus, and particularly to an apparatus having improved operational and maintenance features.
2. Description of the Prior Art
A variety of fluid shear couplings are known in the art and which typically include a driving member received within a working chamber defined by the driven member. Various, specific fluid shear surfaces and mounting means have been proposed. It is an object of the present invention to provide a fluid shear coupling apparatus which has improved operational and maintenance features over those of the prior art.
In U.S. Pat. No. 3,809,197, issued to Clancey on May 7, 1974, there is disclosed a viscous coupling including relatively rotatable input and output coupling members. These coupling members include a plurality of interdigitated lands and grooves which define a shear space therebetween and which are cooperable with viscous shear fluid in the shear space to transmit torque between the coupling members. A temperature-responsive valve means is included for controlling flow of viscous fluid from a reservoir chamber to the shear space. The output coupling member is mounted to a shaft of the input coupling member by means of ball bearings. A similar viscous coupling is disclosed in U.S. Pat. No. 3,856,122, issued to Leichliter on Dec. 24, 1974. The Leichliter coupling includes interdigitated lands and grooves defining a shear space between input and output coupling members. The Leichliter coupling is specifically designed to improve heat dissipation by means of the particular location of the shear surfaces and by the use of cooling fins rotating at the input speed to generate a greater blower action through the fins. Similar fluid shear couplings are disclosed in U.S. Pat. Nos. 3,498,431, issued to Sutaruk on Mar. 3, 1970; 3,323,623, issued to Roper on June 6, 1967; and 3,174,600, issued to Oldberg on Mar. 23, 1965.
The use of an anti-friction coating on portions of a fluid shear coupling apparatus is also known in the art. In U.S. Pat. No. 3,964,582, issued to Mitchell on June 22, 1976, there is disclosed a fan drive hydraulic coupling which includes a polyphenylene sulfide material coated on the sides of the drive or input disc. The material coating functions as an anti-friction and bearing surface. A different type of coating for use in a fluid shear coupling is disclosed in U.S. Pat. No. 3,978,952, issued to Hall on Sept. 7, 1976.
In U.S. Pat. No. 4,004,668, issued to Blair on Jan. 25, 1977, there is disclosed a fluid shear coupling which includes pumping grooves extending across the concentric ridges or lands defining the fluid shear surfaces. These secant grooves extend across the top of the interdigitated ridges of the driving member and of the housing interior to cause the shear fluid to move generally radially for the purpose of inhibiting high temperature build-ups.